After some on and off again erratic behaviour reported in earlier posts, my charger finally quit completely, sometime in the middle of a charging cycle. Opening the unit, obvious was the burnt precharge resistors (in the picture), which also melted some of the relay case. The resistors now measure essentially an open circuit.

Measuring resistances (while in the circuit board) across the bridge rectifier terminals, all resistances are high. Similarly, the Mosfets (i.e. Q7 and Q8) do not measure any obvious shorts. No blown fuses. Could the problem be the Viper chip or whatever else powers the relay, as its de-energizing is what might have caused the resistors to burn up? Although wouldn't everything shut down if the aux power when down?

Would the next step in troubleshooting be replacing the resistors and powering up again to see what happens, for example seeing, if there is aux voltage power? With no batteries connected, the current in the resistors should fall quickly after starting up assuming the transistors are not shorted, so this should be safe enough I imagine.

Learning how to patch and repair PIP-4048 inverter-chargers and Elcon chargers.

After some on and off again erratic behaviour reported in earlier posts, my charger finally quit completely, sometime in the middle of a charging cycle. Opening the unit, obvious was the burnt precharge resistors (in the picture), which also melted some of the relay case. The resistors now measure essentially an open circuit.

Measuring resistances (while in the circuit board) across the bridge rectifier terminals, all resistances are high. Similarly, the Mosfets (i.e. Q7 and Q8) do not measure any obvious shorts. No blown fuses. Could the problem be the Viper chip or whatever else powers the relay, as its de-energizing is what might have caused the resistors to burn up? Although wouldn't everything shut down if the aux power when down?

Would the next step in troubleshooting be replacing the resistors and powering up again to see what happens, for example seeing, if there is aux voltage power? With no batteries connected, the current in the resistors should fall quickly after starting up assuming the transistors are not shorted, so this should be safe enough I imagine.

Attachments

DrDonoh_Burnt_resis 2.jpg (1.27 MiB) Viewed 1062 times

Learning how to patch and repair PIP-4048 inverter-chargers and Elcon chargers.

drdonh;1006362 wrote: Opening the unit, obvious was the burnt precharge resistors (in the picture), which also melted some of the relay case. The resistors now measure essentially an open circuit.

If you didn't power up the charger after the failed charge, that means that the relay opened (the input relay is across the pre-charge resistors, and normally shorts them out except for the first half second or so). It seems likely that the 15 V power supply collapsed (it drives the relay, as well as the power section electronics). My guess is that something shorted the 15 V power supply.

Could the problem be the Viper chip or whatever else powers the relay, as its de-energizing is what might have caused the resistors to burn up? Although wouldn't everything shut down if the aux power when down?

If the red/green LED was still working (for more than 10 seconds or so), then no, the Viper powers the 12 V power supply that runs the processor and LEDs.

Would the next step in troubleshooting be replacing the resistors and powering up again to see what happens, for example seeing, if there is aux voltage power?

I'd first check for a short on the 15 V power rail; see earlier posts for details. Replacing the 150 Ω resistors isn't easy without taking out the main board, which takes some time, patience, and some tools that you might not have handy. If the 15 V power supply doesn't seem shorted (some 325 Ω is normal, from memory), I'd consider applying a current limited power supply set to about 52 V and 0.5 A to the input of the bridge rectifier, bypassing the failed pre-charge diodes for now. You won't need pre-charge as the power supply is current limited. Then check for 15 V and 12 V power, and see if anything gets hot.

With no batteries connected, the current in the resistors should fall quickly after starting up assuming the transistors are not shorted, so this should be safe enough I imagine.

If you don't have a suitable power supply handy, that's probably worth doing. I'd attempt to do a temporary repair of the pre-charge resistors without taking out the main board, to save time and effort. Be ready to disconnect quickly, in case the MOSFETs are shorted and the relay doesn't come on. I'd check for a short on the DC bus first, to save smoking the new resistors.

If the DC bus is shorted, it's a long repair: remove main PCB, remove dead MOSFETs, check for dead driver chips (I find one of U15 or U16 always blows if the MOSFETs blow), and check for blown gate resistors and diodes. I've just done one like this, and it had a fairly high carnage:
* Bridge rectifier
* PFC MOSFETs (at least you don't have this)
* U16
* Several gate diodes and resistors
* U12 (commonly fails when the MOSFETs and one of U15/U16 blow)
* Input relay contacts welded
* I replaced two of the 220 μF capacitors; I suspect that C38 drying out and/or going high internal resistance is the cause of most charger failures that take out the MOSFETs
* R28 (68 Ω in series with the input relay coil) was high resistance

Thankfully, the 12 V power supply, processor, etc were all fine.

My guess for your case, if you find a short on the DC bus, is 4 MOSFETs, U15 or U16, two 10R resistors and two BAW56 diodes, and possibly the 4001 (U12). That may give you an idea how much work is ahead of you, and whether you want to take it on or not.

Learning how to patch and repair PIP-4048 inverter-chargers and Elcon chargers.

The database errors are preventing me from maintaining the original version of this post, which is one of the ones I refer to myself most often. My apologies to readers who may be sick of seeing it.

Warning: if the mains input is connected to actual mains, the "GND" mentioned here is at lethal potential to the ground pin of the mains, and your body. In other words:GND is HOT!
I believe that these jumpers are only intended for use with a current limited power supply of about 52 V.

I've finally sussed out the use of the three main jumpers on the Elcon/TC charger daughter board (the one with most of the chips on it, including the processor and small red LED).

J8: short to disable the PFC stage. This is a good thing when debugging with a 52 V current limited power supply, because the MOSFETs will switch at 50 V rather than 385 V.

J7: Short to force 240 V mains detection. Without this jumper, the mains sensing circuitry will decide that your 52 V power supply is too low, and will disable both the PFC stage, and the PWM stage. So the MOSFETs won't switch at all.

J3: Without a battery detected, the microcontroller won't enable any switching. By inserting a jumper with a 1.8 kΩ resistor (see below), you will get a moderate duty cycle. This is ideal for testing. [ Edit: I used to recommend a 3.3 kΩ resistor for a very low duty cycle, but on some chargers, there isn't enough voltage to get the UC3846 to start generating pulses. ]

So the sensible combination of jumpers is as follows, in order:

1) All jumpers out. 50 V across the main MOSFETs, but they are not switching. Good for finding shorted MOSFETs. Leave the power supply current limit at 0.5 A or less.
2a) Optional. Only J3 in. For the truly cautious, this will give the MOSFETs a short burst of switching, then immediately stop switching them (as it realizes that the mains is not present). You should be able to measure part of the voltage from the next step at the output, slowly decaying. It might be only a half or even a quarter, so a peak of 4-12% of maximum voltage, or 5-16% of nominal voltage.
2b) All jumpers in. 50 V across the MOSFETs, which are now switching. You should see some 15% of maximum rated voltage (about 20% of nominal voltage) at the charger output (negative output terminal and PCB pad, see below). Power supply limit can stay at 0.5 A or less.

At this point, you should be confident that the MOSFETs are switching properly, because the energy in the bus capacitors is about to increase about 8² = 64 times. Use a DSO if there is any doubt. One thing to check is that there is some dead time for both half cycles; test point T34 is for this. Dead time is when this point is low. T34 is awkward to get to under U12, so just use pin 11 of U12 (middle pin). There should always be some time during each half cycles when this test point is low. I like to use both my J3 jumpers (1.8 kΩ and 3.3 kΩ), as well as no J3 jumper at all.

3) J7 in, J8 out, J3 out. Now there should be ~ 385 V on the DC bus (the MOSFET power supply), but the MOSFETs are not switching yet. The power supply current limit needs to be at least 2 A, preferably 2.5 A, to get started. It may take ~10 seconds to get close to maximum bus voltage, at which point the current should fall to around half an amp (it jumps around a lot on my power supply, which is two 26 V supplies in series).
4) J7 in, J8 out, J3 in. Now there should be ~385 V on the DC bus, and the MOSFETs should be switching. The power supply limit needs to be at least 2 A, possibly 3 A. Now you should read about 110% of the maximum rated voltage (about 150% of nominal voltage) at the charger output. This could exceed the voltage rating of the output capacitors; if so, don't leave it running like this for very long. I prefer to start with a 2 A current limit, even though it takes over 10 seconds to reach maximum bus voltage. That gives me a chance to switch off if things don't seem right, and there is a slightly better chance I won't damage too much.

If it passes all this, it's time to reassemble the charger and test with a real battery and mains power.

Here is my collection of jumpers:

Jumpers3.jpg (83.91 KiB) Viewed 1061 times

The jumpers appear to be 2.5 mm spacing, but I used the more commonly available 0.1" header pins (2.54 mm spacing). The slight mismatch makes them stay put without falling out. Note: there is black junk over all of the jumpers, in fact over 95% of the PCB, so you need to clean the area around the jumpers. Also, the holes fill up, which is a royal pain. I use a paper clip to push through the holes. You may need to clean the back of the board where the jumpers come through as well. A wooden chopstick, flat at one end and sharpened at the other, is useful for this. I sharpen the pointy end with a pencil sharpener, and the flat end with a small file. (Thanks for the idea, KennyBobby.)

The two jumpers at the left are shorted; the heatshrink is to keep them together and to make them easier and safer to handle.

Here are the locations of the jumpers, and some close-ups:

Jumper locations broad.jpg (296.85 KiB) Viewed 1061 times

Jumpers J7 J8.jpg (67.43 KiB) Viewed 1061 times

Jumper J3.jpg (75.35 KiB) Viewed 1061 times

GND via.jpg (70.76 KiB) Viewed 1061 times

Power connector.jpg (128.62 KiB) Viewed 1061 times

The power connector on the left of the control board is useful for connecting to ground with a multimeter negative lead or DSO ground lead (though you get tons of glitches when the MOSFETs are firing). I had a plug already made up, but only plugged it into the top pin, so there was no danger of shorting the 15 V power supply. For temporary multimeter negative leads I often use the ground via circled in orange. For +15 V, the top of L1 (in the top left hand corner of the PCB) is handy.

At the output of the driver chips (U15 and U16), you should see ~ 12 V p-p on the low outputs (pin 1), and around 60 V p-p on the high outputs (pin 8). The latter is because you are adding the ~ 48 V from the MOSFETs switching (50 V from the power sless some diode drops), plus the ~ 12 V from the boost power supply (pin 7, this should be a square wave with the low end around 12 V to around 60 V at the top end, about 12 V higher than the MOSFET outputs).

When all is fixed, you should see some DC output, but not necessarily at the actual positive output terminal. This is because the micro doesn't see a battery, and so won't connect the output relay. There is a resistor across the relay, so you should see something at the positive output terminal. But there is a spare relay position (only populated for very low voltage chargers whose output exceeds 20 A), where a multimeter positive lead can be conveniently placed:

Relay pad output.jpg (114.11 KiB) Viewed 1061 times

The negative lead can be placed on the negative output terminal (not interrupted by the relay being open), or the negative output lead if it's still connected.

In my case, I was working on a 288 V nominal unit with a 13:7:8 transformer ratio (many of the transformers seem to have their ratios written on them, particularly the 2 kW units). The :7 and :8 parts add; only the higher two voltage units have this arrangement. Treat it as a 13:15 ratio transformer. Lower voltage chargers will have rations like 13:9 or 25:8. In my case, I expect roughly 15/13 x 50 V = 58 V; I was seeing a little over 60 V.

[ Edit: added sentences re test point T34 and dead time. ]
[ Edit: 2 A is a good value for the final jumper test. ]

Learning how to patch and repair PIP-4048 inverter-chargers and Elcon chargers.

Would the next step in troubleshooting be replacing the resistors and powering up again to see what happens, for example seeing, if there is aux voltage power? With no batteries connected, the current in the resistors should fall quickly after starting up assuming the transistors are not shorted, so this should be safe enough I imagine.

I would check L10 on the main board over by the viper. this has opened on several chargers I worked on.

Learning how to patch and repair PIP-4048 inverter-chargers and Elcon chargers.

Further to my troubleshooting attempts after discovering the pre-charge resistors had burnt out on my charger .....

I temporarily replaced these resistors (soldered overtop actually) with 100 ohm resistors, as these were the closest I had to 150. Plugged the unit in to main power, but with no battery pack load connected, and observed that the relay energizes fairly quickly, there is a brief rise of smoke from the resistors, and the LED status lights start blinking as would be expected. Even after 10 minutes plugged in, everthing seems ok, the resistors are not smoking any more. I measure a small AC voltage across the resistors (~2 volts), but I suppose this should be zero, and is perhaps not normal.

I then try the charger connected to the battery pack and plug in the unit. Again, a small puff of smoke from the resistors, and then, when the other relay that connects the batteries kicks in, and the charging current rises, the resistors start smoking again, and I quickly unplug the unit. The precharge relay is energized during the whole time, as I hear it turn off a few seconds after the main line is disconnected.

I suppose this has to be the relay that is at fault. Yet, the contacts do not look arced out, as in a picture I saw earlier in this thread. I suppose this could even be poor solder contacts for the relay. I only have spare time now and again to work on this, so it will take a few days to investigate this further, especially if I have to lift the board. Thanks to all those who contribute to this thread, as it is very helpful.

Learning how to patch and repair PIP-4048 inverter-chargers and Elcon chargers.

drdonh;1008114 wrote: I temporarily replaced these resistors (soldered overtop actually) with 100 ohm resistors, as these were the closest I had to 150. Plugged the unit in to main power, but with no battery pack load connected, and observed that the relay energizes fairly quickly, there is a brief rise of smoke from the resistors

Yes, I've also seen the puff of smoke from the wrong type of resistor. See this post (and especially one few posts after that one) where I show what type they are from the factory, and what I recommend that they be replaced with. The occasional puff of smoke is OK for a few times while testing.

I measure a small AC voltage across the resistors (~2 volts), but I suppose this should be zero, and is perhaps not normal.

It's definitely not normal. The charger is only drawing about 2.5 watts at this point, so that's about 1.6 Ω of contact resistance. So that's about R₁R₂/(R₁×R₂) = 1.55 Ω with the 50 Ω across it. At full power, that's approaching 10 A across this 1.55 Ω resistance, or nearing 15 V across those 100 Ω resistors, or over 2 W each. They certainly can't take that for long. But the relay contacts would be dissipating up to 15 V × 1.6 Ω = 24 W. So that would be cooking the contacts, or the solder joints, even if the contacts don't appear to be pocked or flashed from arcing.

So it's either really bad soldering under the relay contacts, or more likely the relay needs replacing. This is where I get them from in Australia. Translate that to whereever you get your parts.

Thanks to all those who contribute to this thread, as it is very helpful.

Yes, a special shout out to Kenny and Paul who got the ball rolling, and did the heroic schematic trace.

Learning how to patch and repair PIP-4048 inverter-chargers and Elcon chargers.

kennybobby;900953 wrote: The yellow gunk makes a good tell-tale indicator--it turns brown or black if exposed to a thermal source (and heat makes it easy to crumble off). So if a chip or capacitor has gotten hot it shows up.

Amen to that, brother! I've noticed that a lot of the yellow gunk goes brown, and dismissed it as an aging effect. But now that I've had two chargers go bang when I applied mains power (which is usually after the 2-hour re-assembly job), and it was R3 or C11 both times, I'm starting to respect this browning. What a wonderful repair aid! Now, if only they were easier to get the main board in and out of, they'd be a good repair job.

Now I'm thinking "if it's gone brown, replace the part!".

I've never seen the yellow gunk go black. Do you sometimes get carried away with the heat gun, perhaps?

Learning how to patch and repair PIP-4048 inverter-chargers and Elcon chargers.

I finally figured out how to secure the L15 heatsink firmly, when the bolt and/or slot become worn and the bolt turns instead of being prevented by turning by the slot. L15 is the smaller of the two rectangular inductors on the battery side of the charger, and its heatsink is held between the PCB and the chassis/heatsink with a single M3 bolt, with a hex head, and the chassis/heatsink. The aluminum of the slot wears easily, so this happens a fair bit. I find it hard to source these small hex-head (not hex socket) bolts. With this technique, it's possible to use ordinary countersunk or cheese head bolts. (An alternative might be pan heads that are filed to about 5.3 mm wide on two sides, but I did not have any of suitable length to hand.)

I found that I could jam a large jeweler's flat blade screw driver under the bolt, from the side of the chassis, to jam it into place. Then the usual long-nosed 5.5 mm socket tightens the heatsink with the usual nylock nut. I was previously trying to jam a smaller flat blade above the PCB, just under the nylock nut. But fortunately the bolt for this heatsink is near the edge of the chassis, so it's possible (with this one at least) to access it from the side of the charger. The end of the screwdriver is seen edge-on in the upper part of the diagram.

I hope that readers can figure out what I'm trying to say from the attached diagram. The upper part of the diagram is viewed from the side of the charger, while the lower part is viewed from above.

Attachments

Securing L15.png (36.95 KiB) Viewed 1060 times

Learning how to patch and repair PIP-4048 inverter-chargers and Elcon chargers.

The contacts on the start relay did in fact have a bit of arcing, as seen on the photo. That was enough to fully shut the unit down, eventually. I cleaned up the contacts with a bit of emery paper, and the charger is back to normal. As a recap, the symptom leading up to the final total failure where the unit went totally dead due to burnt pre-charge resistors, was that at random startups, the unit would never reach full charging current, or the current rise was much slower than normal. Perhaps this will be helpful to others in their troubleshooting.

P.S. My electrical repair experience is more with home appliances like toasters and microwaves. Based on the components I see used in those applications, I would never have guessed this start relay is rated at 16A. It did last 9 years, but it still seems kind of small considering all the power for the charger goes through it.

Thanks for everyone's help, as I did go through the whole thread in this venture.

Attachments

DrDonoh_DSCF5606.jpg (214.93 KiB) Viewed 1060 times

Learning how to patch and repair PIP-4048 inverter-chargers and Elcon chargers.